The present invention relates to pipe gaskets for sealing a bell and spigot pipe connection. Specifically the present invention relates to a gasket having a base and a sealing lip which is pressed against the base to form a tight seal by mechanical interaction between the base and the arm.
Pipes used for water supply lines or sewage lines frequently have a bell at one end which receives the spigot of an adjacent section of pipe. Typically, in plastic pipe the bell includes an internal, annular recess in which a gasket is placed to seal the joint between the bell and spigot. The gasket must not only make an effective seal, it must also be relatively simple to install and must retain itself in the recess in the bell, and it must allow the spigot to be inserted relatively easily.
One design that has proven successful in meeting these goals is shown in U.S. Pat. No. 3,173,694 to Nathan, which is incorporated herein by reference. Broadly, this patent shows a pipe gasket comprising a relatively compressible elastomeric base of annular shape. A flexible, conical arm is attached to the leading periphery of the base and tapers inwardly to a sealing lip over the trailing periphery of the base. The arm and base are formed so that as the spigot is inserted into the bell the arm folds over on the base. The base or the arm has a raised, fulcrum portion which contacts the opposite element at approximately its midportion as the arm is folded over. As compression continues the interaction of the arm and the base cause the lip of the arm to kick away from the base and to cause the lip to seal more tightly against the spigot than it would otherwise. The same reaction occurs in the base causing it to seat more firmly in the bell even though it may not be provided with a corresponding lip. Such gaskets have been sold for years by Hamilton Kent Manufacturing Company of Kent, Ohio, and are known as "self energizing" gaskets.